The present invention relates to a telephone set consisting of a handset and a cradle for the handset.
1. Field of the Invention
More particularly, it relates to a lock-releasing mechanism of a telephone handset having a muting function of a mobile or portable radiotelephone set convenient for use when fitted in a vehicle such as an automobile.
2. Description of the Related Art
Telephone sets of this type must be fitted in such a way that the handset cannot fall out of the cradle or cause a vibrating noise when the vehicle such as an automobile is subject to vibration or shock. To this end, commonly the handset is removably fixed by a locking mechanism or the like. Therefore, it is very important for the handling of telephone sets of this type that the handset can be easily placed on the cradle or removed from the cradle and that the structure of the locking mechanism ensures a smooth working thereof.
The telephone transmitter is arranged so that it will always pick up vocal sounds and transmit them to an other party. Thus, when a conversation not desired to be heard by the other party is to be made with any nearly person or when it is intended to block any noise at the first party from the other party, the transmitter is usually covered by the palm of the hand to intercept such speech or noise (namely, muting). Particularly where the telephone set is fitted in an automobile, there will be other cases where such muting is necessary.
Many conventional telephone sets of this type are so arranged that the handset is retained with the receiver-side head surface thereof in contact with the bottom surface of the depressed portion of the cradle, and a locking pawl, lock-releasing mechanism, and lock-releasing button are provided on the cradle. Telephone sets of this type are advantageous in that the handset thereof can be designed to be compact and lightweight. However, since the receiver-side head surface is in contact with the bottom surface of the depressed portion of the cradle, the handset cannot be retained in a stable manner, so that the pushbuttons cannot be easily operated since the handset becomes unstable when they are operated; also the handset cannot be easily replaced on the cradle or removed from the cradle since the lock-releasing button is located on the cradle.
In some of the telephone sets proposed heretofore, the locking pawl, lock-releasing mechanism, and lock-releasing button are all provided on the handset. In any of these types of conventional telephone sets, however, the handset necessarily becomes large and heavy and is not easy to handle.
For the muting operation with a conventional telephone set, especially with an automotive telephone set, it is difficult to cover the transmitter with the palm of the hand since only one hand is usable during speech while the car is being driven; therefore, muting of the voice from the first party is not possible with the conventional automotive telephone set during driving of the car. It has been proposed to provide a dedicated voice muting switch which permits muting of the voice from the first party.
However, provision of such a dedicated voice muting switch independently of the lock-releasing mechanism on the handset will give rise to a safety problem during car driving, whether it is located at a point other than the handset or on the handset itself, and to another problem from the viewpoint of the limited space available for the telephone set.